1. Technical Field
The present invention relates to an ink jet recording method, an ultraviolet-ray curable ink, and an ink jet recording apparatus.
2. Related Art
In the related art, various methods are used as a recording method of forming an image on a recording medium such as paper on the basis of an image data signal. Among them, since an ink jet method of ejecting an ink onto only a necessary image part with low-priced apparatus and directly forming an image on a recording medium, an ink can be used with high efficiency and thus running costs are low. In addition, noise is small and thus the ink jet method is good as a recording method.
In recent years, in an ink jet recording method using an ultraviolet-ray curable ink in which monomers are photopolimerized (cured) by irradiating the monomers with ultraviolet rays, an image with good water resistance and rubfastness can be formed on a recording surface of a recording medium, and thus the method is used for manufacturing of color filters, printing on a printed board, a plastic card, a vinyl sheet, a large-sized signboard, and a plastic part, printing of barcodes or the date, and the like.
An ink used for ink jet recording may include an aqueous ink of a solvent system, an ultraviolet-ray curable ink (UV ink) of a nonsolvent system, or the like. Among them, since the ultraviolet-ray curable ink of the nonsolvent system has a considerably higher viscosity than the aqueous ink of the solvent system, a viscosity fluctuation due to a temperature fluctuation during ejection is great, and this viscosity fluctuation exerts great influence on a variation in a droplet size and a variation in droplet ejection speed and further causes image quality deterioration. Therefore, a technique is disclosed in which, when the ultraviolet-ray curable ink is ejected, the ink is heated so as to reduce a viscosity and is then ejected.
For example, JP-A-2003-200559 discloses a UV ink in which, since the UV ink has a higher viscosity than general ink at room temperature and is thus required to be ejected in a low viscosity state by heating the ink inside a recording head so as to maintain a set target temperature (a set temperature necessary for the ink to have a viscosity in which the ink can be ejected), the UV ink is varied by adjusting a heating temperature such that the ink viscosity is 7000 mPa·s to 500 mPa·s in a condition of 5° C. and the ink viscosity is 20 mPa·s to 3 mPa·s in a condition of 80° C. (paragraphs [0034], [0041] and [0042] of JP-A-2003-200559).
However, the UV ink disclosed in JP-A-2003-200559 has a problem in that members of the head deteriorate due to the heating. In addition, since the UV ink has a very high viscosity, if the ink is to be ejected without heating, ejection stability or ejection amount stability worsens.